lxc_by_ip.sh

#!/bin/bash

: '
This script lists all running containers on a Proxmox host along with their
Container ID (CTID), IP addresses, and hostnames. If an IP 
address is provided as a command-line argument, the script will highlight (in red)
the IP in the output. 
The loopback interface and IPv6 link-local addresses are omitted.

Usage: 
./lxc_by_ip.sh [IP address]

Parameters:
[IP address]  - An optional parameter. If provided, the script will highlight
                this IP address in the output. 
'

# ANSI escape code for highlighted (red) text
highlight="\e[31m"

# ANSI escape code for resetting text color
reset="\e[0m"

# Loop over all running containers and print their IDs, IP addresses, and hostnames
for i in $(pct list | awk '/running/{print $1}'); do
    ips=$(pct exec $i -- hostname -I)
    ips="${ips%"${ips##*[![:space:]]}"}"  # Remove trailing spaces
    hostname=$(pct exec $i -- hostname)
    if [ -n "$1" ]; then
        # If this container's IP address matches the highlight IP, print it in red
        if [[ $ips =~ $1 ]]; then
            ips=${ips//$1/${highlight}$1${reset}} # Replace the matching IP with a highlighted version
            echo -e "CTID: $i, IPs: ${ips}, Hostname: $hostname"
        else
            echo "CTID: $i, IPs: ${ips}, Hostname: $hostname"
        fi
    else
        echo "CTID: $i, IPs: ${ips}, Hostname: $hostname"
    fi
done

Helps you find which running container (LXC) on a Proxmox host has a certain IP address.